feat: 实时消息与管理端运营能力

新增群聊/私信与公共 WebSocket 总线，站长用户内容档案，并将通知与待审角标改为推送驱动；同步精简管理仪表盘并修复主题换肤 DOM 冲突。

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/handler/setting.go

@@ -3,7 +3,9 @@ package handler
 import (
 	"errors"
 	"net/http"
+	"strings"
 
+	"github.com/freefire/jiang13-bbs/realtime"
 	"github.com/freefire/jiang13-bbs/service"
 	"github.com/gin-gonic/gin"
 )
@@ -40,5 +42,11 @@ func (h *Handlers) UpdateSettings(c *gin.Context) {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": "保存站点设置失败"})
 		return
 	}
-	c.JSON(http.StatusOK, gin.H{"ok": true, "accent": req.Accent})
+	// 归一化后的值实时广播：所有在线客户端立即热换肤，无需 F5 或等轮询
+	saved := strings.ToLower(strings.TrimSpace(req.Accent))
+	h.Hub.BroadcastAll(realtime.Envelope{
+		Type: realtime.EventSettingsChanged,
+		Data: map[string]string{"accent": saved},
+	})
+	c.JSON(http.StatusOK, gin.H{"ok": true, "accent": saved})
 }